Usually a vacuum cleaner is provided with a cleaning device for filtering the dust-laden air sucked in with the dust and particles collected in a dust cup and discharging the filtered air. That is, the cleaning device of the traditional vacuum cleaner is actually a filtering device. Therefore, the users should have the filter devices cleaned or replaced after using for a while. Otherwise, fine dust may clog the filtering apertures of the filtering devices, thereby increasing the resistance of the vacuum motor or even burning it out. That will bring troubles to the users, and will affect the performance and lifetime of the vacuum cleaners.
In recent years, according to the principle of cyclone separation, some vacuum cleaner manufacturers use a cyclone separator to replace the filtering device and achieve favorable results. Therefore, that has been widely used in vacuum cleaners. The cyclone separator is provided in its dust cup with a conical cyclone cylinder, which is provided vertically at the top end with an airflow outlet pipe connected through with the air outlet of dust cup. The cyclone cylinder is also provided at its bottom end with an opening for dust falling into the dust collecting case at the bottom of the dust cup. The airflow inlet pipe is provided on the side wall of the upper portion of the cyclone cylinder and along the tangential direction, so that air flow carrying dust will generate cyclone in the cyclone cylinder. Dust and particles will fall along the side wall of the cyclone cylinder into the bottom of the dust collecting case under centrifugal force, and the filtered air flow is discharged out of the dust cup upwards through the airflow outlet pipe.
However, with the reinforcement of the environment protection consciousness of the customers, vacuum cleaners of single stage can not meet their requirements. Vacuum cleaners which have better filtering performance and cleaner air discharged and have not secondary pollution are required. However, the vacuum cleaners with two stages of separating apparatus may result in defects that the cyclone raises dust and cleaning the dust is inconvenient.
Moreover, the customers of different area in the international market have different requirements. Some customers, e.g. supermarkets, need vacuum cleaners of lower price and middle-level performance, and a single cyclone separation is usually required in the filtering performance of the dust cup of the vacuum cleaner. Some customers, e.g. high-end customers, require vacuum cleaners of high filtering performance. Therefore vacuum cleaners of two cyclone separation stages and the second cyclone separation carried in multiple cyclone cylinders are required. Therefore, different dust cups need developing for the design of the same contour of vacuum cleaners, thereby resulting in increased production cost and waste in design and production resources. In order to solve the above problems, a vacuum cleaner which can meet the forgoing two different requirements and won't affect the contour is required.